Hey Gaz - from the uk here!
To to Pets at home (yeah yeah I know) and get the liquid
ammonia and liquid
nitrite API test kit. They employees should be able to point it out to you.
You can buy prime on ebay if you really need it.
Now an explanation of the
nitrogen cycle as I understand it:
Fish waste and uneaten food turns into ammonia. In a new tank there isnt enough bacteria to cope with ammonia and it will start to poison your fish. The safest way to combat this is 25% water changes every day or to buy tetra safestart and cross your fingers.
Once the bacteria has grown enough to cope with the ammonia, it breaks it down into nitrites which is also poisonous to the fish but the good news is you are into phase 2 of the cycle so keep up with water changes.
When your tank has finished cycling you will have readings of 0 ammonia 0 nitrItes and should have 5-10 nitrAtes. As your
nitrate reading is high, personally I would add 1-2 live plants which will also help by eating the ammonia and nitrite and when the tank is cycled it will help you with nitrates, thats if you want live plants of course

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See if you have a maidenhead aquatics near you. they are brilliant and usually know what they are on about.
www.fishkeeper.co.uk is their site

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